Length matching traces on different layer - bug?

I think the trace length matching tool, when used is ignoring half the trace because it’s routed on another layer.

On the first screenshot you can see that the selected trace is 2280 mil long.

On the second screenshot:
When using the length matching tool, parts of the trace is getting deleted, and half of it gets ignored as the tooltip now says that the trace is 1720 mil long.


is this a bug, or am i doing something wrong?

Also, length tuning differential traces is impossible, as half of it simply dissapears

First, is your KiCad version up to date?

Application: KiCad (64-bit)

Version: (6.0.0-rc1-114-gb471945224), release build

22.11.2021.

I just restarted the software, and the bug with the disappearing differential trace went away, then after trying using it again it started happening again, and the tool is still measuring the wrong lengths.

Ivanilevmcu, I think you found a bug. Unfortunately this is a KiCad users forum, the developers sometimes read it, sometimes - not. It’s easy to miss. Could you report this in the KiCad Gitlab’s issue tracker? An example PCB showing the problem would be very useful for us too.

Tom

Since the reported issue was confidential, I will also comment here:

The “disappearing trace” bug should be fixed now. However, there is something important to note about KiCad’s length tuner that is the main reason why you see different lengths reported:

KiCad today only supports tuning point-to-point routed nets. In other words, a connection between two (and only two) pads. The design @ivanilievmcu shows uses what appears to be a memory interface using “fly-by” topology. KiCad cannot properly tune the length of this topology, or other branching topologies, at least not today (V6).

In the future, we plan to improve the length tuner so that it supports these topologies, and you can choose the length to measure by specifying the driver and receiver pads, for example. Until then, this limitation is important to know about, because the length tuner will find a single “point-to-point” portion of the route and report the length of only this portion. The “routed length” display at the bottom just adds up all the track segments on the net, so you will see a larger number here for these topologies.